Wheel driving mechanism for grinding machines



Sept. 7, 1937. c. G. FLYGARE 2,092,714 WHEEL DRIVING MECHANI'SM FOR GRINDING MACHINES Filed March 50, 1936 nunuunnu Patented Sept. 7, 1937 UNITED STATES PATENT OFFICE WHEEL DRIVING IVIECHANISM FOR. GRIND- ING MACHINES Application March 30, 1936, Serial No. 71,552

4 Claims.

The invention relates to a wheel driving mechanism for grinding machines.

One object of the invention is to provide a grinding machine with a constant grinding surface speed. Another object of the invention is to provide a drive for a grinding wheel which automatically compensates for reduction in diameter of the grinding wheel. Another object of the invention is to provide a driving mechanism for a grinding wheel permitting the grinding wheel to be used with maximum efliciency until it is discarded. Another object of the invention is to facilitate shop computations. Another object of the invention is to make grinding a more standardized operation. Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements and arrangements of parts, as will be exemplified in the structure to be hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawing, in which is shown one of many possible embodiments of the mechanical features of this invention,

Figure 1 is a vertical transverse sectional view through aplain cylindrical grinding machine having the grinding wheel driving mechanism of the invention incorporated therein;

Figure 2 is a rear elevation of the grinding machine showing the wheel driving motor and its mounting;

Figure 3 is an enlarged detail view of the wheel driving disk in axial section. Referring first to Figure l, I provide by way of example a cylindrical grinding machine having a front base It) and a rear base II but the inven tion is applicable to other types of machines, for example surface grinders and other types.

Formed in the front base H] are a pair of ways l2 and 13 for the support of a work carriage 14.

The work carriage l4 has ways l5 and I6 for the support of a headstock, not shown, and a tailstock 20. On the tailstock 26 is a movable center 2| in a sleeve 22, the position of which can be adjusted and then locked by means of a handle 23. This construction may be the same as that usually provided in cylindrical grinding machines and 50 the like, and the headstock, not shown, may have a driving plate and a headstock center for the rotation of a cylindrical shaft or other cylindrical work piece to be ground.

I provide a cross feed hand wheel and micrometer mechanism 25 of any usual, customary or desired type for controlling the position of the work piece and grinding wheel relative to each other. That shown herein is not described in detail as any desired construction in this respect maybe provided and furthermore automatically acting cross feed mechanism may be provided. The mechanism 25 includes a ratchet wheel 30 which has a pinion gear portion 3! driving a gear 32. The ratchet wheel 30 and pinion gear 3| are mounted on a stud 33 which is supported by a bracket 34 fastened to the machine base Ill. 10 Passing through the bracket 34 and journaled therein is a long screw shaft 35 to which is keyed the gear 32. Shaft 35 has a screw portion 36 which is engaged by a half nut 31 fastened to the under side, of a cross slide 38. 15

The machine base ll provides suitable transverse ways, not shown, in which rest guide portions 40 and 4| (Fig. 2) of the cross slide 38. Referring now to Figures 1 and 2, cross slide 38 has a massive upstanding portion 43 with parallel 20 vertical sides 44 and 45. A trunnion or rock shaft 46 passes through the massive portion 43 and into holes 41, 48 of opposite legs 49 and 50 of a motor support bracket 51 for a motor 52 which is secured to the bracket 5|. The motor 25 52 has an armature shaft 53 upon which are mounted two wheels 54 and 55.

Referring now to Figure 3, the wheel 54 comprises a central hub 56 keyed to the shaft 53,

from which hub radiate a plurality of spokes 51. 30

The spokes 51 support an outer rim 58 having a radial face 59, as shown, and also a cylindrical shoulder 60. The wheel comprises a central hub 6| similar to the hub 56 and which is also keyed to the shaft 53. Likewise spokes 62 extend 35 from the hub 6| to a rim 63 having likewise a radial face 64 and a cylindrical shoulder 65. There are a plurality of holes 66 in the rim 58 and there are a plurality of holes 61 in the rim 63. In addition, there are a plurality of radial 40 slots 68 intersecting the holes 61 in the rim 63.

A pair of annular disks 10, 10 of rubber fit between the radial surfaces 59 and 64 and are. supported by the cylindrical shoulders and 65, and are held in position by bolts 1| passing through holes in the annular disks 10 and through the holes 66 and 61. The bolts ll have heads '12 with tongues 13 on the under side thereof which fit in the grooves 68. This prevents the bolts 1| from turning and nuts 14 se- 50 cure the bolts in position and draw the rims 58 and 63 against the rubber disks 15 to clamp the disks firmly in position. Preferably I provide a Washer 15 between the wheels 54 and 55 and I provide a nut 16 and washer 11 to hold the mit the same angular movement.

wheels 54 and 55 on the shaft 53 against the shoulder 18 thereon. The spokes 51 and 62 can be relied upon to bend slightly under the pressure of the bolts II when the annular rubber washers are being clamped in position, and the desired amount of clearance prior to tightening may be provided. It will be understood that the provision of two annular disks 18 of rubber is by way of example, and I could provide one, three or any greater number thereof.

Rubber disks 18 are preferably of resilient rubber, that is to say vulcanized with an amount of sulphur considerably less than 20% and to a soft condition, and furthermore they may be reinforced with fibrous material or the like. I prefer to use a soft rubber with layers of cloth or cord therein, of the general structure found in pneumatic tires for automobiles.

The machine provides a grinding wheel head 88 of any usual or preferred construction and a grinding wheel spindle 8| which is journaled in suitable bearings and any desired or known practice in this respect may be adopted. To the wheel spindle 8| is fastened a grinding wheel 82 and wheel 82 is representative of any type or construction of grinding wheel, for example one particularly adapted for grinding of shafts or the like in a plain cylindrical grinding machine.

The annular disks l8, 10 rest against the periphery of the grinding wheel 82. Adjustable pressure holds the disks against the grinding wheel and the disks l0 and wheels 54, 55 move towards the grinding wheel as it diminishes in diameter due to wear thereof. Referring now K to Figure 1, I provide a depending ear 85 on the bracket 5| to which is fastened a screw rod 86 having a forked end 81 through which and through the ear 85 extends a pin 88. The rod 86 passes through a hole 89 and a hole 98 in the wheel head 88. The hole 89 is considerably larger than the rod 86 to provide for angular motion of the rod. The hole 98 fits the rod 86 with a fairly close fit excepting that the hole 98 should be countersunk from both sides to per- The rod 86 is threaded at the right-hand end and has thereon a nut 9| operated by hand wheel 92. The nut 9| extends through an enlarged opening 93 in the front side of the wheel head 80. A spring 94 is located on the rod 86 and at the lefthand end is backed up by a portion of the wheel head 80 adjacent the hole and at the other end thrusts against a washer 95 which abuts the nut 9|. Thus the spring 94 urges the rod 86 to the right and thus tends to rock the bracket 5| on the trunnion or rock shaft 46 to cause the Wheels 54 and 55 to approach the grinding wheel 83 and to press the annular rubber disks I0, 18 against the periphery of the grinding wheel 82. Furthermore, the tension can be increased by turning the hand wheel 92 and as the grinding wheel 82 wears, the driving wheels 54 and 55 follow it up. Thus whenever the motor 52 is energized, the grinding wheel 82 is rotated and the peripheral speed of the grinding wheel 82 is relatively constant and actually substantially the same as the peripheral speed of the disks 10, 10.

The grinding wheel 82 is hard and rough but wears down to a smaller diameter by reason of the work which it performs in grinding work pieces and further by reason of a dressing operation from'time to time to true its face. Assuming that a six thousand surface feet per minute speed was found efiicient under certain specified conditions for grinding a particular shaft, the proper motor 52 and the right size of wheels 54 and 55 can be selected to give that exact surface speed. The grinding wheel will inevitably wear smaller until it has to be replaced and it should be understood that there is normally a considerable difference in the diameter of a grinding wheel just before it is discarded and the same grinding wheel when it was new. The disks 10, 18 virtually mesh with the periphery of the grinding wheel insomuch as the soft substance thereof conforms itself to the rough surface of the grinding wheel. Insomuch as the disks 18, 18 are resilient, there is not the tendency for them to wear and, furthermore, with a substantial pressure between wheel and disks there is very little slippage at the point of contact. While the disks I0, 10 may wear to a certain extent in time, it is contemplated that they will be replaced often and the construction provided allows for their ready replacement. Furthermore they are relatively cheap.

A grinding operation has many variables, for example hardness of the stock being ground, speed of rotation of the work, diameter of the work, composition of the grinding wheel with respect to the particular abrasive used, the type of bond, grade hardness of the wheel, speed of traverse if any, etc. The calculation of the various variables for the most efiicient production on a particular job is a factory problem of intrinsic difficulty due to the many variables. The existence of a variable which is such not only as to the particular operation but also during the course of many operations is a particularly annoying factor in such calculations. Therefore, by eliminating the variability of surface speed of the grinding wheel, I have considerably simplified certain shop calculations. It will be understood that under modern factory conditions the motor for operating the grinding wheel will in many cases be a three phase induction motor or a synchronous motor and will with difllculty be regulated so far as its R. P. M. is concerned; direct current which is more readily controllable by a rheostat being unavailable in most factories today.

It will thus be seen that there has been provided by this invention apparatus in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawing is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. In a grinding machine, a work table or carriage, means to hold the work thereon, a grinding wheel, a spindle for said grinding wheel, a wheel head providing journals for the spindle, precision cross feed mechanism to produce a relative advance between the wheel head and the work carriage or table, a driving mechanism for the grinding wheel comprising a prime mov er, a friction disk engaging the periphery of the grinding wheel, a connection between the prime mover and the friction disk, and means for urging the friction disk against the grinding wheel which will maintain them in contact as the grinding wheel is reduced in diameter in use, thereby to provide for a constant peripheral speed of the grinding wheel.

2. In a grinding machine as claimed in claim 1 the combination with. the parts and features therein specified of means on the table or carriage to hold the work piece for rotation.

3. In a grinding machine as claimed in claim 1 the combination with the parts and features therein specified of ways for reciprocating the table or carriage in a direction normal to the cross feed.

4. In a grinding machine as claimed in claim 1 the combination of the parts and features therein specified of means on the table or carriage mounting the work piece for rotation and ways for the table or carriage permitting it to be moved in indirection normal to that of the cross feedL j CARL G. FLYGARE. 

